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Infocom. 4. ea 2013. szept. 30.1 Infokommunikációs rendszerek – Infocommunication Systems Lecture 4. előadás Kódolás, nyalábolás, kapcsolás Coding, multiplexing,

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Presentation on theme: "Infocom. 4. ea 2013. szept. 30.1 Infokommunikációs rendszerek – Infocommunication Systems Lecture 4. előadás Kódolás, nyalábolás, kapcsolás Coding, multiplexing,"— Presentation transcript:

1 Infocom. 4. ea szept Infokommunikációs rendszerek – Infocommunication Systems Lecture 4. előadás Kódolás, nyalábolás, kapcsolás Coding, multiplexing, switching Takács György

2 Infocom. 4. ea szept Where we are now in study (tele-, info-) communications systems? Networks are working systems of terminals, nodes and links The basic technologies in links (wireline and wireless) have been discussed Node functions (multiplexing, switching, signalling, demultiplexing) will be discussed today

3 Infocom. 4. ea szept. 30.3

4 4

5 5 Analog modulation systems- (AM) Amplitude modulation The momentary amplitude of the carrier is proportional to the momentary amplitude of the modulating signal

6 Infocom. 4. ea szept Analog modulation systems- (AM)

7 Infocom. 4. ea szept The spectrum of the AM in the case of discrete f m modulation frequency

8 Infocom. 4. ea szept Frequency modulation systems- (FM) The momentary frequency of the carrier is proportional to the momentary amplitude of the modulating signal

9 Infocom. 4. ea szept Frequency modulation systems- (FM)

10 Infocom. 4. ea szept The spectrum of FM modulated signal in the case of discrete f m modulation frequency

11 Infocom. 4. ea szept Digital modulation methods – Amplitude Shift Keying (ASK)

12 Infocom. 4. ea szept Digital modulation methods – Binary Phase Shift Keying (BPSK)

13 Generation of BPSK Infocom. 4. ea szept x  ~ Carrier signal BPSK t

14 Infocom. 4. ea szept Digital modulation methods – Constellation Diagram / BPSK

15 Infocom. 4. ea szept Eye diagram as a basis for demodulation of BPSK signal Received BPSK signal x Carrier signal comparator 1,0,1,0 ∫ Eye diagram

16 Infocom. 4. ea szept Digital modulation methods –Qadrature Phase Shift Keying (QPSK) Two carriers: sine wave (Q) and cosine wave (I) The modulated signal is the sum of the two components One symbol is two bits

17 Infocom. 4. ea szept Digital modulation methods –Qadrature Phase Shift Keying (QPSK)

18 Infocom. 4. ea szept Digital modulation methods –Qadrature Phase Shift Keying (QPSK)

19 Infocom. 4. ea szept Digital modulation methods –Qadrature Phase Shift Keying (QPSK) 1

20 Infocom. 4. ea szept Digital modulation methods –Qadrature Amplitude Modulation (QAM) Two carriers: sine wave (Q) and cosine wave (I) The modulated signal is the sum of the two components Different amplitude and differnt phase values for one symbol 16QAM means: one symbol is four bits

21 Infocom. 4. ea szept Digital modulation methods –Qadrature Amplitude Modulation (16QAM)

22 Infocom. 4. ea szept Digital modulation methods –Qadrature Amplitude Modulation (16QAM)

23 Infocom. 4. ea szept Digital modulation methods –Qadrature Amplitude Modulation with channel noise

24 Infocom. 4. ea szept Why to use sophisticated modulations -- like QAM? To put more bits into the standard medium –twisted pair cable –ADSL, Gigabit Ethernet, –coaxial cable – digital TV, HDTV, INTERNET, –Radio – GSM, satellite TV and radio program broadcasting Efficient use of spectum (the radio spectrum is a limited resource)

25 Bit error rate as a function of signal to noise ratio using BPSK modulation Infocom. 4. ea szept

26 Channel capacity as a function of signal to ratio at different modulation system. The reference is the BPSK Infocom. 4. ea szept

27 Infocom. 4. ea szept Multiplexing vs. switching City ACity B Trunks for active calls only

28 Infocom. 4. ea szept Multiplexing principles To reduce transmission costs To utilize higher bandwidth „Framing” and „packing” of information TDM -- Time Division Multiplexing FDM -- Frequency Division Multiplexing CDMA -- Code Division Multiple Access WDM -- Wavelength Division Multiplexing Mixed

29 Infocom. 4. ea szept TDM principles I. PCM frame 4.50 ábra (Pulse Code Modulation) 125 µs

30 Infocom. 4. ea szept TDM principles II. PDH hierarchy 4.51 ábra Plesiochronous Digital Hierarchy

31 Infocom. 4. ea szept TDM principles III. PDH hierarchy 4.51 ábra

32 Infocom. 4. ea szept SDH hierarchy SDH – Synchronous Digital Hierarchy VC – Virtual Container (multiplexing level) STM-N Synchronous Transport Modules (line signal level) POH – path overhead (control and supervisory information) POH+Payload=VC A number of VCs can packaged into a larger VC

33 Infocom. 4. ea szept Transport modules RSOH – Regenerator Section Overhead MSOH – Multiplexer Section Overhead AU Pointer – Administrative Unit Pointer (specifies where the payload starts) Duration of STM-1 module is 125 µs

34 Infocom. 4. ea szept General Transport Module ábra

35 Infocom. 4. ea szept

36 Infocom. 4. ea szept

37 Infocom. 4. ea szept SDH Network elements DXC – Digital Cross Connect ADM – Add-drop Multiplexer TM – Terminal multiplexer

38 Infocom. 4. ea szept Example of a physical network

39 Infocom. 4. ea szept FDM principles

40 Infocom. 4. ea szept TDM/FDM channel architecture as used in GSM

41 Infocom. 4. ea szept FDM in Cable TV network (US Standard)

42 Infocom. 4. ea szept Variable bit-rate data transfer within TDM time- slots

43 Infocom. 4. ea szept The Spread Spectrum Concept

44 Infocom. 4. ea szept General Model of Spread Spectrum Digital Communication System

45 Infocom. 4. ea szept Frequency_Hopping Spread Spectrum FHSS

46 Infocom. 4. ea szept FHSS A number of channels are allocated for FH The transmitter operates in one channel at a time for fixed time interval (Tc) During that interval, some number of bits or a fraction of a bit are transmitted (signal elements) The time interval of signal elements Ts The sequence of the channels used is dictated by spreading code Both transmitter and receiver use the same code to tune into a sequence of channels in synchronisation

47 Infocom. 4. ea szept Transmitter of the FHSS System

48 Infocom. 4. ea szept Receiver of the FHSS System

49 Infocom. 4. ea szept Slow FHSS using Multi Frequency Shift Keying Tc>Ts (in this case 4 subfrequencies for 2 bits)

50 Infocom. 4. ea szept Fast FHSS using Multi Frequency Shift Keying Tc

51 Infocom. 4. ea szept Example of Direct Sequence Spread Spectrum DSSS

52 Infocom. 4. ea szept DSSS system Transmitter

53 Infocom. 4. ea szept DSSS system Transmitter

54 Infocom. 4. ea szept Comparison of FDM –TDM -- CDM TDMAFDMA

55 Infocom. 4. ea szept Principle of WDM

56 Infocom. 4. ea szept Principle of WDM

57 Infocom. 4. ea szept Switching techniques in public networks

58 Infocom. 4. ea szept The Group Switch interconnects incoming and outgoing time slots

59 Infocom. 4. ea szept Time and space switches

60 Infocom. 4. ea szept The principle of TST switching

61 Infocom. 4. ea szept Group switch with 512 multiple position

62 Infocom. 4. ea szept Connections to the local exchange

63 Infocom. 4. ea szept Node for packet switching

64 Infocom. 4. ea szept Packet node structure

65 Infocom. 4. ea szept Connection oriented transfer phases: Connection setup (setup packet with complete address, Logical Channel Number stored in each node Data transmission (only LCN in the header) Release Connectionless transport: Destination address in the header Path selection in the nodes Different packets have different delay The order of received packets has no guarantee

66 Infocom. 4. ea szept ATM cell switching principle Fixed cell (packet) length – 53 bytes 5 octets header, 48 octet payload

67 Infocom. 4. ea szept Why connection oriented packet switching? Connectionless – only best effort quality (www = world wide waiting) Connection oriented – QoS guarantee is possible Quality measures: delay, jitter, packet loss.

68 Infocom. 4. ea szept Content of ATM cell header

69 Infocom. 4. ea szept Segmentation and multiplexing of different Services in cell based systems

70 Infocom. 4. ea szept The principle of ATM switching

71 Infocom. 4. ea szept VP (Virtual Path „coarse level addressing”) and VC (Virtual Channel „fine level addressing”)

72 Infocom. 4. ea szept The structure of the ATM switch

73 Infocom. 4. ea szept Signalling principles in circuit switching

74 Infocom. 4. ea szept Signalling flow in a telephone call

75 Infocom. 4. ea szept Signalling for distributed supplementary services or a mobile telephone call

76 Infocom. 4. ea szept Signalling in packet switched networks

77 Infocom. 4. ea szept Principles of Common Channel Signalling CCS

78 Infocom. 4. ea szept

79 Photonic Fibre Switches In free-space devices, the light is focused from the input fibre, deflected by a micro-mirror (typically several times) and finally launched into the output fibre. The Micro- Electro-Mechanical Systems (MEMS) technology is mature and can produce switch matrices with up to hundreds of input and output ports (128x128 or 256x256), low insertion loss (IL), very low cross talk, low power consumption, millisecond switching speed, and broadband operation. The mirrors can typically be controlled electro-magnetically, electro-statically or by piezoelectric actuators. Infocom. 4. ea szept

80 Operational principle and example of 3D MEMS array Infocom. 4. ea szept collimator


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